Computers today. Гурьянова В.И. - 12 стр.

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mathematical statement of this versatility: Any computer with a certain mini-
mum capability is, in principle, capable of performing the same tasks that any
other computer can perform. Therefore, computers with capability and complex-
ity ranging from that of a personal digital assistant to a supercomputer are all
able to perform the same computational tasks as long as time and storage capac-
ity are not considerations.
A general purpose computer has four main sections: the arithmetic and
logic unit (ALU), the control unit, the memory, and the input and output devices
(collectively termed I/O). These parts are interconnected by buses, often made
of groups of wires. The control unit, ALU, registers, and basic I/O (and often
other hardware closely linked with these) are collectively known as a central
processing unit (CPU). Early CPUs were comprised of many separate compo-
nents but since the mid-1970s CPUs have typically been constructed on a single
integrated circuit called a microprocessor.
Control unit
The control unit (often called a control system or central controller) di-
rects the various components of a computer. It reads and interprets (decodes) in-
structions in the program one by one. The control system decodes each instruc-
tion and turns it into a series of control signals that operate the other parts of the
computer. Control systems in advanced computers may change the order of
some instructions so as to improve performance.
A key component common to all CPUs is the program counter, a special
memory cell (a register) that keeps track of which location in memory the next in-
struction is to be read from. Since the program counter is conceptually just another
set of memory cells, it can be changed by calculations done in the ALU. Adding
100 to the program counter would cause the next instruction to be read from a place
100 locations further down the program. Instructions that modify the program 
mathematical statement of this versatility: Any computer with a certain mini-
mum capability is, in principle, capable of performing the same tasks that any
other computer can perform. Therefore, computers with capability and complex-
ity ranging from that of a personal digital assistant to a supercomputer are all
able to perform the same computational tasks as long as time and storage capac-
ity are not considerations.
      A general purpose computer has four main sections: the arithmetic and
logic unit (ALU), the control unit, the memory, and the input and output devices
(collectively termed I/O). These parts are interconnected by buses, often made
of groups of wires. The control unit, ALU, registers, and basic I/O (and often
other hardware closely linked with these) are collectively known as a central
processing unit (CPU). Early CPUs were comprised of many separate compo-
nents but since the mid-1970s CPUs have typically been constructed on a single
integrated circuit called a microprocessor.

                                       Control unit

      The control unit (often called a control system or central controller) di-
rects the various components of a computer. It reads and interprets (decodes) in-
structions in the program one by one. The control system decodes each instruc-
tion and turns it into a series of control signals that operate the other parts of the
computer. Control systems in advanced computers may change the order of
some instructions so as to improve performance.
      A key component common to all CPUs is the program counter, a special
memory cell (a register) that keeps track of which location in memory the next in-
struction is to be read from. Since the program counter is conceptually just another
set of memory cells, it can be changed by calculations done in the ALU. Adding
100 to the program counter would cause the next instruction to be read from a place
100 locations further down the program. Instructions that modify the program



                                         12

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